In internal combustion engines, critical torsional vibrations can increase noise, reduce gear life and cause premature engine failure. For example, the torque being transmitted to drive a camshaft of an engine starts out low and increases until a cam lobe activates a valve. The higher the loads required to activate the valve the greater the torsional loads which must be overcome by the camshaft. The constant variation of loads on the camshaft from high loads when the force of the valve springs and the springs of the unit injectors are being compressed to no load when the springs are expanded and the valves are closed results in a wide range of working forces acting on the camshaft. Thus, the results of the torsional load causes a windup of the camshaft and once the resisting load is overcome the windup of the camshaft will cause the camshaft to unwind or backlash. The camshaft becomes an instantaneous driving member rather than a driven member further inducing impact loads on the driving and driven members resulting in increased noise, reduced gear life and premature engine failure.
An example of a coupling used for dampening torsional oscillations is disclosed in U.S. Pat. No. 2,895,316 issued to Jan Kloud, et.al. on July 21, 1959. In this coupling, an elastic coupling with mechanical springs for dampening torsional oscillations is shown.
In another example a viscous dampening means is disclose in U.S. Pat. No. 3,528,265 issued to Leo device a coupling mechanism is adapted to reduce and absorb vibratory motion in a drive shaft. The dampener has a plurality of openings having a pair of similar, oppositely disposed pistons therein. Each piston is spring-biased inwardly for slidably receiving a connecting pin therebetween. In addition there is a passage leading to at least one chamber formed by the walls of the cylindrical opening and pistons for introducing a viscous fluid therein. Each chamber has an outlet to discharge a measured amount of fluid and controlling the amount of fluid in each chamber.
The art as cited above does not recognize a further problem which exists with dampeners having contacting components therein and having relative motion therebetween. Such relative motion causes friction, noise, wear and decreases the life of the components having relative motion therebetween.
The present invention is directed to overcome one or more of the problems as set forth above.